text: By the late 1860s, Wislicenus devoted his research to organic chemistry.  His work on the isomeric lactic acids from 1868 to 1872 resulted in the discovery of two substances with different physical properties but with an identical chemical structure.  He called this difference "geometrical isomerism".  He would later promote J. H. vant Hoffs theory of the tetrahedral carbon atom, believing that it, together with the supposition that there are "specially directed forces, the affinity-energies",  which determine the relative position of atoms in the molecule, afforded a method by which the spatial arrangement of atoms in particular cases may be ascertained by experiment. While at Würzburg, Wislicenus developed the use of ethyl aceto acetate in organic synthesis. However, he was also active in inorganic chemistry, finding a reaction for the production of sodium azide. He was the first to prepare cyclopentane in 1893